Reflecting system for deviating a convergent pencil of imagning rays



March 25, 1941. GUNTHER 2,236,403

TING A CONVERGBNT PENCIL OF iuAeING RAYS REFLECTING SYSTEM FOR DEVIL Filed Jan. 25, 19

Inventor: 71': 425-: M

Patented Mar. 25,1941 Q UNITED STATESPATENT Oi-FiCE REl-IECTING srs'rmf ron nsvm'rme .agi wenoan'r PENCIL or meme Norbert Gunther, Jena, Germany, solicitor to the firm of Carl zeiss, Jena, Germany Application January 25, 1940,

- serial No. 315,600 r In Germany February 9,1939

1 Claim- (clsax-2.2)

, The paths of imaging rays of numerous optical differences cannot be avoided between the exmeasuring instruments are deviatedin the measpansion coeiflcients 'of the prism-stool and the uring plane from their original direction by ocular reflecting system which as a rule consists pmeans of mirror systems or reflecting prisms. As of glass. In addition to this it has not been pos- 5 an example of such instruments the known sible so far to entirely solve the problem of a rangeflnders are referred to. The construction perfect connection between these twoparts, on ofa rangeiinder, for example, is as follows. An account of amechanlcal attachment by pressure outer tube surrounds all optical parts of the incausing strains whilst cement-layers were subject strument. At the ends of the outer tube the to the influence of moisture and heat.-

pencils of imaging rays enter through reflecting The invention is based on the idea-to construct 10 systems by which these pencils are deviated a reflectingsystem to deviate a convergent peninto the direction of the basis of the rangeflnder. oil of imaging .rays, the reflecting system to be The central part of the outer tube carries aplate permanently connected with a measuring mark to which-besides some elements not coming into and with a carrier for fltting the said system into consideration here-one or two eyepieces are so an optical measuring instrument, the construe-- attached that their axes stand at right angles to tion to be carried through in such a way that the basis. Within the outer tube an inner tube, whatever relative displacements may be occain two of its cross sections, is supported in unisioned by the aforesaid influences affect the versal joints thus resulting in any flexures of the measuring mark and the image point belonging outer tube not being transferred in general upon to it in exactly the same manner. Failing to sat- 20 the inner tube. In its ends the inner tube carisfy this condition a dislocation-as a result of ties-the.rangeiinder-obiectives and in-its central the;displacements-wili-occur:between the measpart it assumes a box-like shape. In this boxuring mark and the conjugate image point and like part a so-called prism-stool is so attached cause inaccurate readings. The said problem with screws that, for adjusting purposes, and prior can be solved if the carrier, in accordance with to the screws being finally stiffened-it can be the invention, is secured in the measuring inshifted by small amounts at right angles to the strument by means of an axle whose center line axis of the inner tube. The prism stool consists in the virtual reflected image of the axial point of the same material as the inner tube and conof the plane of the measuring mark stands vertains the ocular reflecting system which is protically on that particular plane where the devivided with one or several measuring marks and ation of the axial ray takes place, which as a rule which deviates the pencils of imaging rays into applies to the measuring. plane. The carrier,obthe direction of the ocular axis or axes. viously. Shou d e made i e e ter a as Whilst heat unilaterally applied to the outer the reflecting system proper, or at least of a matube causes flexures of the outer but not of the terial having the same expansion coeflicient, so inner tube, the latter is subjected to the effect of as to avoid the occurrence of strains between the the daily and seasonal fluctuations in temperacarrier and the reflecting system which-caused ture as well as of mechanical influences (shocks, by fluctuations in temperature-are likely, for etc.). In the event of the material not being instance, to bring about deformations of the re- 4 exactly the same for all parts and not homogenefleeting plane. Carrier, reflecting system and ouswithin the individual parts alterations in the measuring mark accordingly form a rigid body form will occur as a result of fluctuations in temand whatever displacements may occur in this perature. These alterations will cause changes body within the measuring instrument can only in the spacing between the measuring marks and consist of rotational movements about the said 4 the reflecting surfaces belonging to the two paths axle. However in the case of all such movements 4 of imaging rays. A change in spacing amountthe point of the axis lying in the measuring plane ing to more than one thousandth of a millimetre always represents the reflected image of the axial is sufllcient to invalidate the demands for acpoint of the plane of the measuring mark, and curacy required of rangeflnders. The same apthe measuring mark and its conjugate image plies if one reflecting surface or both of them are point are subject to identical displacements. dislocated by the said amount at right angles to Displacements in the axle itself in the direction the axis of the inner tube. Whereas a specially of the axial ray of the pencil of imaging rays encareful treatment of the material of the inner .terlng the reflecting system have no detrimental tube and of the prism-stool makes it possible to effect as long as the 'observers eye does not attain the necessary degree of homogeneousness, change its normal position, i. e., when the a 55 of the eye coincides with the optic axis of the eye-piece for observing the measuring mark and connected therewith is easily overcome by the accommodation of the observing eye.

It is the displacements in the axle occurring at right angles to the aforementioned direction which would cause reading errors as in the case of these displacements However, flexures of this kind, as emphasized at the outset are prevented by the employment of an inner tube which does not partake in the flexures of the outer tube to any detrimental degree,

Experiments have shown that the detrimental ing plane. The axis of rotation of the reflecting system must accordingly always stand perpendicular upon that respective plane verge into a This point e represents the virtual reflected image or a point strument in question.

The second constructional example (Figs. 2 to 4) is an eyepiece reflecting system for a stereoscopical rangeflnder. In this case the reflecting element is represented by a glass prism 71., whose reflecting surface inclines at an angle of 45 rela- A reflecting system pencil of imaging rays, a measuring mark. means for supporting said reflecting system in an optisaid reflecting system of that point in which said axis intersects the measuring plane.

NORBERT fiNTHER.

point e of the axis of the pencil of for deviating a convergent l 

